I will here share the recipe I use for making crochet circles and balls of any size.
So you don’t have to lookup specific recipes for the size of your choice.
- SC: Single crochet (American term, see here for difference between British and American terms)
- INC: 2 single crochets in one stitch
- DEC: 2 stitches crocheted into one (Guide here)
- [Number]: Means how many stitches should there will be in total when done with a ‘row’
Since the balls are just circles that we continue working on, we will start with the circles.
You would probably notice that we follow a pattern of using the number 6. We will increase and decrease according to this number.
Side note: If you don’t have it already, a counter is really nice to keep track of how many rows you have done.
First you start off with a magic circle with 6 stitches (guide here).
Then you follow this formula for each row:
((N – 1) SC, INC) * 6
Where N equals row.
Example for the first 4 rows:
1. ((N – 1), INC) * 6 => ((1 – 1) SC, INC) * 6 => (INC) * 6 
2. ((N – 1), INC) * 6 => ((2 – 1) SC, INC) * 6 => (1 SC, INC) * 6 
3. ((N – 1), INC) * 6 => ((3 – 1) SC, INC) * 6 => (2 SC, INC) * 6 
4. ((N – 1), INC) * 6 => ((4 – 1) SC, INC) * 6 => (3 SC, INC) * 6 
And you just keep doing this until you have the desired size.
Tip: Every row just adds 1 more SC before the increase.
You start with the circle recipe until you have the desired size, then you will shape it into a ball.
Important: When you are working on the last 2 rows, you should put filling inside the ball.
Where K equals number of rows from the circle.
For example if you did 4 rows for the circle:
K = 4
So: 1-4: SC
Then you will do decreases to close off the ball.
Where you can use the following formula:
(Y SC, DEC) * 6
Where Y equals ((Current stitches in row) – 12)/6.
So for example with our 4 row circle with 30 stitches, we will begin with:
Y = ((Current stitches in row) – 12)/6 => ((30) – 12)/6 => 18/6 => 3
So: (Y SC, DEC) * 6 => (3 SC, DEC) * 6 
Then for the next row we have 24 stitches.
Y = ((Current stitches in row) – 12)/6 => ((24) – 12)/6 => 12/6 => 2
So: (Y SC, DEC) * 6 => (2 SC, DEC) * 6 
And for the next 2 rows it would be:
(SC, DEC) * 6 
(DEC) * 6 
Tip: The number of SC before the decrease, just gets decremented by 1.
Tip: If you look closely you will notice the decreasing is the reverse of the incrementing in the beginning.
You then cut off a tail of the yarn and close off the last 6 stitches with a sewing needle, by passing the yarn through the outer loops of the stitches and then pulling it tight.
Sew the remaining yarn tail into ball, by putting the needle all the way through the ball and let the yarn stay inside the ball hidden away.
You now have generic recipes for making crochet circles and balls.
You might also want look at this post, to see different way of joining the circles.
For more crochet related content, you can go here.